1. Field of Invention
The present invention relates to a semiconductor device, more particularly to a memory device.
2. Description of Related Art
A Dynamic Random Access Memory (DRAM) is an essential element in many electronic products. In a memory cell, a channel region lies underneath the gate and between the source and the drain. A voltage imposed upon the gate controls the flow of current from the source to the drain within the channel region. Such memory devices are widely used and are easily formed of silicon and silicon oxide.
Silicon is a semiconductor material. In contrast, silicon oxide is an excellent insulator. The interface between silicon and silicon dioxide can be made with extremely high electrical quality, that is, with a very low density of electronic interface states within the energy bandgap of silicon. However, silicon has its limitations such as low carrier mobility and conductivity. In recent years, the conductivity and mobility of silicon can be increased by an ion-doping process. Unfortunately, in a recessed access device, the ion-doping process is difficult to specifically and uniformly form an ion-doped layer between the gate and the substrate.
In this regard, an improved semiconductor structure and manufacturing method for the semiconductor device are still necessary to solve the problems met in the art.